Fuel cells produce electricity from chemical reactions. The chemical reactions typically react hydrogen and air/oxygen as reactants, and produce water vapor as a primary by-product. The hydrogen can be provided directly, in the form of hydrogen gas, or can be derived from other fuels, such as butane or other hydrocarbon liquids or gasses, that can be reformed to isolate hydrogen gas for the reaction. A Solid Oxide Fuel Cell (SOFC) is often a solid state device which employs a solid oxide ceramic material such as Yttria Stabilized Zirconia (YSZ) as the electrolyte, which remains solid at normal operating temperatures—typically in the range of 800° C.—making it impermeable to gas transport. At these temperatures, the electrolyte is a good conductor of electrically charged oxygen ions, and the SOFC takes advantage of this property to generate and extract electrical current from the reaction between fuel and air via oxygen ion transport through the electrolyte.
Solid oxide fuel cell assemblies employ a pair of porous electrodes separated by a solid electrolyte member to extract energy from the fuel. The electrodes provide a large number of chemical reaction sites which enable electrically charged oxygen ions to be transported through the electrolyte, creating an electrical potential that can be harnessed by an external device. The electrodes employed by SOFCs have included electrodes formed from thermally sintered ion conducting particles. To form these sintered electrodes, a coating or layer of conductive particles may be laid over or applied to the solid oxide electrolyte and then the electrolyte and the particles can be heated, typically to a temperature above 1000° C. Optionally, this deposition and heating process can take place over several iterations, with the end result being a sintered layer of hard electrode material formed over and adhered to the electrolyte. Typically this process is used to form electrodes on both sides of the electrolyte, so that the process yields a layer of electrolyte that had electrodes on either side.
Although these processes for forming the sintered electrodes can work well, they do require a temperature that is sufficiently high to cause or to risk structural damage to the oxide electrolyte. The risk of damage increases with the fragility of the electrolyte layer. A problem today is that the electrolyte layer used in SOFCs seems to perform better if applied as a very thin layer of material over a substrate that acts as a mechanical support. The thin layer of electrolyte provides a greater efficiency per volume of material than a thicker layer. This can yield greater power densities for the fuel cell device. However, as layers grow thinner, the electrolyte becomes more susceptible to thermal damage, and thus—in an iterative process of thermal cycling that heats thin layers of electrolyte to relatively high temperatures—can fail as the thermal energy can warp or otherwise ruin the electrolyte layer.
Thus, there is a need in the art to provide improved methods for manufacturing SOFCs that have thin layer solid electrolytes, and to provide SOFCs having electrodes that are more reliably manufactured.